Tiziana Ferrari Quality of Service Support in Packet Networks1 Quality of Service Support in Packet Networks Tiziana Ferrari Italian National Institute for Nuclear Physics INFN - CNAF

Tiziana Ferrari Quality of Service Support in Packet Networks2 Overview Problem statement technical solutions: –ATM –RSVP and RSVP to ATM SVC mapping –differentiated services (diffserv) Diffeserv in detail Diffserv: a case study Diffserv test activities (TF-TANT) comments

Tiziana Ferrari Quality of Service Support in Packet Networks3 Quality of Service Heterogeneous networks –capacity –transmission technology –bottlenecks congestion and lack of transmission guarantees heterogeneous application requirements –interactive: telnet, remote X sessions, web browsing –non-interactive and packet loss tolerant: ftp, mailing –delay sensitive: real time applications (e.g. remote control) –delay variation sensitive and packet loss: voice over IP, videoconferencing –... Quality of Service

Tiziana Ferrari Quality of Service Support in Packet Networks4 Solutions Cell based networks: –ATM (permanent and/or switched connections) IP based networks: –RSVP (resource ReSerVation Protocol) and integrated services heterogeneous networks: –RSVP to ATM SVC mapping (IP and ATM) –differentiated services

Tiziana Ferrari Quality of Service Support in Packet Networks5 Differentiated services Why diffserv? –new technology –independent of layer 2 technologies –interoperability between independent national research networks (different requirements, infrastructures, policies and management) –traffic aggregation –scalability: no reservation state maintained in the routers –no signalling –QoS for networks not ATM based RFC 2474: Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 headers RFC 2475: An Architecture for Differentiated Services RFC 2598: An Expedited Forwarding PHB RFC 2597: Assured Forwarding PHB Group cont.

Tiziana Ferrari Quality of Service Support in Packet Networks6 Scheduling Scheduling: queue service policy for differentiated treatment of packets among queues Examples of packet scheduling algorithms: –simple priority queue (high priority queues have the highest priority, arrival rate < departure rate, low priority traffic starvation is possible) –weighted round robin queuing (queues serviced in round robin fashion, service time proportional to the weight) –weighted fair queuing (minimum rate guaranteed per class, service time of each packet in each queue is a function of the packet size and of the queue weight. Current service time is updated every time a packet is sent) –class based queuing (maximum rate per class is configured)

Tiziana Ferrari Quality of Service Support in Packet Networks7 Congestion management and service enforcement: policing Customer Premise PolicySpecification Network Edge Packet Classifier and Policer Policing: traffic which exceeds a given rate threshold is treated differently from conforming traffic. E.g. Exceeding packets can be dropped, re-marked, transmitted as best-effort etc. Policing is deployed for service level agreement enforcement: - to limit the input rate at the edge - at the boundary between domains to guarantee a fair deployment of the service among different domains

Tiziana Ferrari Quality of Service Support in Packet Networks8 Differentiated Services: Case Study

Tiziana Ferrari Quality of Service Support in Packet Networks9 Characterisation of the application Characterisation needed to identify the requirements of the application: service definition 1. Hardware of the trigger: remote control - ROBIN - –few transactions (low bandwidth), TCP traffic on a limited well-known set of TCP ports, IP address of the server known –client - server, one connection to a server at a time  low paket loss, delay sensitive application, reliability, burst tolerance 2. Monitoring of quality and correctness of the results of the analysis - ROOT - –exchange of analysis results (root object) –low bandwidth consumption –client - server, IP address of the server is known  bandwidth guarantee, more tolerance to packet loss

Tiziana Ferrari Quality of Service Support in Packet Networks10 Diffserv testing and QoS measurement

Tiziana Ferrari Quality of Service Support in Packet Networks11 Test network

Tiziana Ferrari Quality of Service Support in Packet Networks12 Equipment Test workstations traffic generators (3 SmartBits, Netcom System loan) ATM switches in the test sites cabletron ethernet switch DS capable platforms : –CISCO: C7200 or C7500 (partial CISCO loan) –IBM: IBM 2212 and IBM 2216 (2 routers in 5 sites, IBM donation) –Linux –Cabletron (LAN switch) –(Nortel, Torrent)

Tiziana Ferrari Quality of Service Support in Packet Networks13 Comments Diffserv building blocks: already supported by several vendors diffserv: no changes in applications required diffserv goal: simplified approach to QoS for its support in backbones from today good interim test results diffserv in the future: –Packet Over Sonet (POS) vs ATM –VLL vs ATM permanent connections

Tiziana Ferrari Quality of Service Support in Packet Networks14 Comments (cont) Issues –effects of high degree aggregation? More testing needed –interoperability between different platforms: effect on end-to-end services? –performance of marking, classification and scheduling at high speed? –Tools for service monitoring…. –Diffserv in production? 1 year?